Methods are proposed for determining the structural and energetic effects of acid stable phosphorylation of specific seryl residues in the various types of calf thymus histone, particularly fl. Recent work strongly suggests that the regulation of transcription may arise through changes in the packing and coiling characteristics of nucleohistone and chromatin, which are brought on, in turn, by cyclic AMP mediated phosphorylation of histones. How directly these three phenomena, transcription, chromosome structure and histone phosphorylation are connected is not completely clear at the present time; however, association of the latter two processes is thought to result directly from alterations in the local charge density in the chromosome, induced by phosphorylation or dephosphorylation, thereby affecting the degree of coiling. Histone fl has up to four sites for phosphorylation, and would seem to be a good candidate for the regulation of chromosome coiling. A histone fl phosphokinase and phosphatase from calf liver have been recently purified in this laboratory, and will be examined as senstivie probes of changes in histone and nucleohistone structure associated with phosphorylation and dephosphorylation. An exploratory investigation of the substrate specificities of these enzymes may reveal something of the structural assembly of chromosomes and the mechanism of chromosomal coiling and uncoiling. A second approach to this question involves an examination of the anti-fl/fl and phosphorylated fl cross reactivity, to be conducted in collaboration with a nearby laboratory with considerable experience in making antibodies. A third approach involves an investigation of the energetic effects of fl phosphorylation, through detailed analyses of derivative melting profiles of nucleohistone and phosphonucleohistone complexes.